The present invention relates to a lid gripping device for automated handling lids of sample vessels, the lids comprising a spigot to be grasped by the lid gripping device, and the lid gripping device is provided with a collet chuck for gripping the spigot of a lid wherein the lid gripping device comprises a positioning element for actively actuating the collet chuck.
Such lidded sample vessels are employed in analytical systems as used in health research, food analysis, environmental analysis, molecular biology and other fields in which contamination of sample substances needs to be reliably avoided. Such vessels and their corresponding lids are known e.g. from DE 44 12 286 A1 and EP 0 734 769 A1.
These lids comprise a cylindrical stopper including a shell wall and a bottom wall. Arranged in the middle of the bottom wall is a vertically protruding spigot by which the lid may be grasped by the lid gripping device. One known lid gripping device (EP 0 734 769 A1, FIG. 7) comprises a collet chuck for gripping the spigot, it functioning according to the principle of a mechanical pencil.
The lid gripping device comprises a tubular housing in a vertical arrangement in which at the lower end a sleeve protruding downwards is shiftingly mounted. Arranged in the sleeve is the collet chuck which is surrounded by a annular element. Shiftingly mounted in the annular element is the collet chuck which opens when shifted downwards by the annular element and closes when shifted upwards in the annular element.
This known lid gripping device functions as follows:
The lid gripping device is mounted from above by its sleeve on a sample vessel. Pressing the lid gripping device downwards urges the sleeve into the housing or lowers the collet chuck together with the annular element within the sleeve so that the collet chuck comes into contact with the spigot. In this action a first spring is tensioned, exerting a first pressure point.
In further pressure from above the collet chuck is urged downwards against the action of a second spring by the annular element so that it opens and is pushed over the spigot.
When a second pressure point is overcome a latching mechanism reduces the pressure exerted downwards by shortening the extent within the lid gripping device, as a result of which the collet chuck grasps the spigot. Since the second spring is still tensioned the annular element is urged downwards and the collet chuck contracted with the spigot clamped therein. Lifting the lid gripping device then removes the lid from the sample vessel.
The latching mechanism is configured similar to that as used in ball pens which latch every time a pressure pulse is applied between an expanded and contracted position respectively.
In mounting the lid on the sample vessel the latching mechanism translates back into its expanded position, as a result of which the collet chuck is urged downwards by the annular element, it opening and releasing the spigot or lid, this requiring a further pressure point to be overcome.
It is intended to use such lid gripping devices in conjunction with automated robotic devices (FIG. 5 of DE 44 12 288 A1).
Setting the forces to be exerted in overcoming the corresponding pressure point has turned out to be difficult, however. Although making the setting with a considerable excess force is basically possible in ensuring reliable actuation of the lid gripping device, this results in the long run in the actuating means of the robotic device being considerably strained and in mechanical distortion of the robotic device in persistent operation which in turn with increasing inaccuracy may result in malfunctioning in gripping or releasing the lids as well as detrimenting other functions of the robotic device.
Disclosed by CH 671 526 A1 is a pipetting device comprising a collet having a pair of arms with which pipettes may be positively grasped at annular beads. For releasing the engagement between the collet and a pipette a spreader sleeve is provided with which the collet may be splayed so that the pipette falls out of engagement. A pipetting device provided with such a collet which holds the pipette solely by its clamping effect fails to be suitable as a gripping device for automated handling sample vessel lids since the lids close off in part very tight and then may only be removed from the sample vessels with great exertion. To enable such high forces to be applied the collet would have to be configured extremely stiff, as a result of which correspondingly high compressive forces would need to be overcome in gripping. It is, however, also possible that the lids may be removed very easily, especially when the lids have already been mounted on a sample vessel several times.
In addition to this the pins for gripping the lids become clogged from frequent handling of the lids thus making a positive grip as needed in the pipetting device impossible in long-term use.
The object of the invention is to provide a lid gripping device for automated handling of sample vessel lids comprising a collet chuck operating on the principle of a mechanical pencil and suitable for use in a robotic device.
This object is achieved by a lid gripping device provided with a collet chuck for gripping the spigot of a lid wherein the lid gripping device comprises a positioning element for actively actuating the collet chuck. Advantageous aspects read from the sub-claims.
The collet chuck of the lid gripping device in accordance with the invention may be actively opened, as a result of which a spigot of a lid may be clasped and grasped by the collet chuck with no compressive force whatsoever.
Reactuating the collet chuck releases the lid from the lid gripping device, again without any pressure point whatsoever needing to be overcome.
In addition, providing an actively actuated collet chuck permits detection of a standby condition in which no lid is grasped and a gripping condition in which a lid is grasped due to the different positions of the collet chuck in the standby condition in which no lid is grasped and a gripping condition in which a lid is grasped.